CFM56-7B T25 probe question
 

chaps,


there has been a number issues of the CFM56-7B having throttle roll backs due to erroneous signals to FADEC due to icing of the T25 probes. I had this discussion with another chap who said that the probe wasn't heated i.e. there is no heating element. It was my understanding that there is and there is a corresponding circuit breaker to match. does anyone have a schematic to show the probe is heated. I do not recall it was heated by engine bleed.


look forward to the responses from the brains trusts!

Bit late, but are you sure is it T25 problem? This sensor is located btw. booster and high pressure compresor inlet, too hot place for icing IMHO.

As it's a combined temp/pressure sensor surely heating it would be a problem
here's the URL link.

https://www.slideshare.net/mobile/cc...fm56-7-fueloil

https://image.slidesharecdn.com/cfm5...?cb=1401834956

Just checked possible ∆T trough LP section and I am really surprised how low is on idle N1. Table is from 56-3, which is bit different, but with same number of stages. PT25 is used for fuel metering and HPTACC schedule. Presure sensing at this station is optional, for engine trend monitoring only. The temperature for both channels is sensed by heated platinium wires with no extra anti-ice.

http://imageshack.cz/images/2016/06/...us_dT25.md.jpg